Need a bit more information. How are you trying to start the program, thru the menu? The 'bar in the lower right', would that be the 'progress' indicator. In the menu properties on my computer, which doesn't have this problem, the command is - rhythmbox %U

Thanks for the reply, I've opened via terminal, alt+f2, favorites, the panel, the mint menu... all the same. Yes, it's the progress bar. At the moment rhythmbox is freezing at every start, not just the first any more...